(function (win, lib) {
    var doc = win.document;
    var docEl = doc.documentElement;
    var metaEl = doc.querySelector('meta[name="viewport"]');
    var flexibleEl = doc.querySelector('meta[name="flexible"]');
    var dpr = 0;
    var scale = 0;
    var tid;
    var flexible = lib.flexible || (lib.flexible = {});

    if (metaEl) {
        console.warn("将根据已有的meta标签来设置缩放比例");
        var match = metaEl
            .getAttribute("content")
            // eslint-disable-next-line no-useless-escape
            .match(/initial\-scale=([\d\.]+)/);
        if (match) {
            scale = parseFloat(match[1]);
            dpr = parseInt(1 / scale);
        }
    } else if (flexibleEl) {
        var content = flexibleEl.getAttribute("content");
        if (content) {
            // eslint-disable-next-line no-useless-escape
            var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
            // eslint-disable-next-line no-useless-escape
            var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
            if (initialDpr) {
                dpr = parseFloat(initialDpr[1]);
                scale = parseFloat((1 / dpr).toFixed(2));
            }
            if (maximumDpr) {
                dpr = parseFloat(maximumDpr[1]);
                scale = parseFloat((1 / dpr).toFixed(2));
            }
        }
    }

    if (!dpr && !scale) {
        // eslint-disable-next-line no-unused-vars
        var isAndroid = win.navigator.appVersion.match(/android/gi);
        var isIPhone = win.navigator.appVersion.match(/iphone/gi);
        var devicePixelRatio = win.devicePixelRatio;
        if (isIPhone) {
            // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
            if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
                dpr = 3;
            } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
                dpr = 2;
            } else {
                dpr = 1;
            }
        } else {
            // 其他设备下，仍旧使用1倍的方案
            dpr = 1;
        }
        scale = 1 / dpr;
    }

    docEl.setAttribute("data-dpr", dpr);
    if (!metaEl) {
        metaEl = doc.createElement("meta");
        metaEl.setAttribute("name", "viewport");
        metaEl.setAttribute(
            "content",
            "initial-scale=" +
            scale +
            ", maximum-scale=" +
            scale +
            ", minimum-scale=" +
            scale +
            ", user-scalable=no"
        );
        if (docEl.firstElementChild) {
            docEl.firstElementChild.appendChild(metaEl);
        } else {
            var wrap = doc.createElement("div");
            wrap.appendChild(metaEl);
            doc.write(wrap.innerHTML);
        }
    }

    function refreshRem() {
        var width = docEl.getBoundingClientRect().width;
        // 最小1366px，最大适配2560px
        if (width / dpr < 1366) {
            width = 1366 * dpr;
        } else if (width / dpr > 2560) {
            width = 2560 * dpr;
        }
        // 设置成24等份，设计稿时1920px的，这样1rem就是80px
        var rem = width / 24;
        docEl.style.fontSize = rem + "px";
        flexible.rem = win.rem = rem;
    }

    win.addEventListener(
        "resize",
        function () {
            clearTimeout(tid);
            tid = setTimeout(refreshRem, 300);
        },
        false
    );
    win.addEventListener(
        "pageshow",
        function (e) {
            if (e.persisted) {
                clearTimeout(tid);
                tid = setTimeout(refreshRem, 300);
            }
        },
        false
    );

    if (doc.readyState === "complete") {
        doc.body.style.fontSize = 12 * dpr + "px";
    } else {
        doc.addEventListener(
            "DOMContentLoaded",
            // eslint-disable-next-line no-unused-vars
            function (e) {
                doc.body.style.fontSize = 12 * dpr + "px";
            },
            false
        );
    }

    refreshRem();

    flexible.dpr = win.dpr = dpr;
    flexible.refreshRem = refreshRem;
    flexible.rem2px = function (d) {
        var val = parseFloat(d) * this.rem;
        if (typeof d === "string" && d.match(/rem$/)) {
            val += "px";
        }
        return val;
    };
    flexible.px2rem = function (d) {
        var val = parseFloat(d) / this.rem;
        if (typeof d === "string" && d.match(/px$/)) {
            val += "rem";
        }
        return val;
    };
})(window, window["lib"] || (window["lib"] = {}));
